US Marine Corps Major General Eric Austin (right) and Philippine Army Major General Marvin Licudin pose at Camp Aguinaldo. AP

Nearly 18,000 troops are taking part in the annual exercises dubbed Balikatan, or "shoulder to shoulder" in Filipino, which for the first time will include a live-fire drill in the South China Sea, which Beijing claims almost entirely.

The drills follow Monday's conclusion of a three-day Chinese military exercise that simulated targeted strikes and a blockade of self-ruled, democratic Taiwan, which Beijing considers part of its territory.

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Balikatan will include military helicopters landing on a Philippine island off the northern tip of the main island of Luzon, nearly 300 kilometres (180 miles) from Taiwan, and the retaking of another island by amphibious forces.

It will be the first time the exercises have been held under President Ferdinand Marcos, who has sought to strengthen ties with the United States after his predecessor Rodrigo Duterte trashed the alliance.

Boosting military tactics

About 12,200 American, 5,400 Filipino and just over 100 Australian soldiers will participate in the two weeks of Balikatan exercises -- about twice as many as last year.

Filipino and US troopers salute during opening ceremonies for the joint military exercise in Quezon City. AP

About 50 leftwing protesters staged a rally outside the opening ceremony venue, calling on the Philippine government to scrap the exercises.

As part of the exercises, troops will stage an amphibious landing on the western island of Palawan, the closest Philippine landmass to the Spratly Islands, where Beijing and Manila have rival claims.

The Americans will also use their Patriot missiles, considered one of the best air defence systems in the world, and the HIMARS precision rocket system, which has helped Ukrainian forces fighting the Russian invaders.

The two armies originally planned to fire live rounds at sea off the northern province of Ilocos Norte, about 355 kilometres from Taiwan's south coast, but later on had to move it further down the South China Sea, Philippine Army Major-General Marvin Licudine said.

Protesters take part in a rally in front of Camp Aguinaldo military headquarters in Quezon City, Philippines. AP

The original site was "not sufficiently prepared" for unloading the needed equipment, he added.

The new venue is less than 300 kilometres east of the Chinese-held Scarborough Shoal.

The exercises will enhance "tactics, techniques and procedures across a wide range of military operations," said Philippine military spokesman Colonel Medel Aguilar.

Soon after the opening ceremony in Manila, the Philippine defence and foreign ministers will jointly meet their US counterparts in Washington.

Agence France-Presse